/*
 * Copyright (c) 2011 Obix Labs Limited
 * Redistribution and use in source and binary forms, 
 * with or without modification, are permitted provided 
 * that the following conditions are met:
 * 
 * 		Redistribution of source code must retain the above 
 * 		copyright notice, this list of conditions and the 
 * 		following disclaimer.
 *
 * 		Redistribution in binary form must reproduce the 
 * 		above copyright notice, this list of conditions 
 * 		and the following disclaimer in the documentation 
 * 		and/or other materials provided with the distribution.
 * 
 * 	THIS SOFTWARE IS PROVIDED "AS IS," WITHOUT A WARRANTY OF 
 * 	ANY KIND. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS 
 * 	AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF MERCHANTABILITY, 
 * 	FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, 
 * 	ARE HEREBY EXCLUDED. OBIX LABS LIMITED ("Obix Labs") AND ITS 
 * 	LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE 
 * 	AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR 
 * 	ITS DERIVATIVES. IN NO EVENT WILL Obix Labs OR ITS LICENSORS BE 
 * 	LIABLE FOR ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, 
 * 	INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE 
 * 	DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF 
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 * 	SOFTWARE, EVEN IF Obix Labs HAS BEEN ADVISED OF THE POSSIBILITY OF 
 * 	SUCH DAMAGES.
 */
package com.obixlabs.commons.util;

import java.util.HashSet;
import java.util.Set;

/**
 * <p>
 * Encapsulates the set difference operator, written as <i>'A-B'</i>.
 * When applied to two sets <i>'A'</i> and <i>'B'</i>, it will return 
 * the values in the set <i>'A'</i> which are not in <i>'B'</i>. 
 * </p>
 */
public class SetDifference extends SetOperator
{	
	@Override
	public<T> Set<T> evaluate(Set<T> lhs, Set<T> rhs)
	{
		Set<T> result = new HashSet<T>();	
		if (lhs !=null)
		{
			for (T element : lhs)
			{
				if (rhs==null || !rhs.contains(element))
					result.add(element);
			}
		}		
		return result;
	}
}